Process of forming printing-plates.



W. W. KIRBY.

PROCESS OF FORMING PRINTING PLATES.

APPLICATION FILED OCT. 28, l9l5.

m1 9,33%; Patented Mar. 13, 1917.

x V /\\)l rrni strains .rnT F WALLACE KIRBY, OF WASHINGTON, DISTRICT OFCUL'UMBIA', ASSIG-INQE, BY MESNE ASSIGNMENTS, TO THE RAPID PROCESSLITHOGBAPH COMPANY, iNQ, A CORPOEA- Tron, or DELAWARE.

PROCESS OF FOENIING PRINTING-PLATES.

Specification of Letters Patent.

Application filed ctob er 28, 1915 Serial No. 58,443.

To all whom it may concern:

Be it known that I, \VALLACE W. Kinny,

a citizen of the United States, residing at \Vashington, in the Districtof Columbia, have lnvented certain new and useful Improvements 1nProcesses of Forming Printing-Plates, of which the following is adescription.

The invention relates to new and useful improvements in the process ofmaking printing plates, and more particularly a metal printing platehavinga plane printing surface. I l

Prior to my invention. efforts have been made to produce a printingplate by coating the same with a sensitized film, exposing the sameunder the design to be reproduced and subsequently developing thedesign. Didi (-ulties have been experienced, however, in obtaining aclear cut and well defined reproduction of the design on the plate.

An bbject of the present invention is to devise a process of treatingthe plate whereby the sensitized film may be removed from the plate andthe non prmtmg surface finished, leaving a printing surface on the platewhich is a clear cut and well defined reproduction of the originaldesi'; 1. M

Figure 1 is a sectional \lOW through a plate having a sensitized filmthereon; and

Fig. 2 is a view of the same-after the un-. exposed portions have beenwashed outand I 7 been exposed to the light; and 1n order that thefilmtreated to form a crust thereon.

The invention consists b oadly in apply; ing a suitable sensitized filmto a ngtal plate, exposing said sensitized surfaceyto light and *ashingout the unexposed portions covered by the design, subsequently treatingthe plate s as to thoroughly' clean 7 the printing surface of anypossible traces of the film and also soi'tenn'ig the film to facilitateits removal. from the plate. After the film has been softened. thesurface of the,

film is hardened or formed with a slight crust, over wluch 1s plaredacoating of a fatty acid-resisting substance and then the plate is washedorotherwise subjected to a mg a. grained metal plate '1 either ofalumnigpin or zinc by applying thereto a sensitized 1n 2 other suitablebase mixed with ammonium bichromate, potassium bichromate, or any othersuitable chemical .which will produce sensitive film, capable of beingrendered insoluble by light. This film is, .of course, dried.

Patented Mar. as, test.

which may be made of glue or any- The design to be reproduced on theprint- '7 ing plate is made on a transparent sheet or substance byanysuitable opaque liquid, and

this original drawing is useddirect in the production of the printingplate, thus eliminating the camera and negative. T he original drawingor design is placed on the sensitized plate and exposed to light. Theexposed parts of the film are rendered insoluble by the action ofthelight thereon, while the unexposed parts ofthe film beneath thedesign remain soluble and maybe 'ashed oil by water after the exposurehas been made. After the plate has been washed. 1 apply a dye such asviolet dye which is soluble in alcohol which causes the subject ordesign indicated at 3 in the drawing to appear very clearly, providing aproper exposn re has been made.

subjected thelplate to the solution of potassium hydrate treatment, Inext apply alcohol until all the violet coloring leaves theplate.

The primary purpose of the alcohol is "to snrface-harden or crust thesoftened film as indicated at 4 in Fig. 2 of the drawing so that acoating of an acid-resisting substance such as an asphaltum solution beapplied to the plate without saidv substance applied to the plate, itadheres very closely to the cleaned printing surface and forms a thincoating over the film.

When the plate is subjected to the hydrochloric acid solution, the acidpenetrates the relatively thin asphaltum coating on the film andundercuts the film so that it may be readily removed, leaving the platecoated with the asphaltum solution only at the part or parts containingthe design or subject. The plate is then finished in the manner wellknown in this art.

From the above, it will be apparent that the three essential features ofmy invention consist: first, in the thorough cleansing of the printingsurface corresponding to the subject or design prior to'the applicationof the acid-resistingsubstance thereto; second, the softening of thebase or film prior to the applying of the asphaltum coating thereto sothat the same may be subsequently readily removed by the acid treatment;and third, surface-hardening of the film or forming a.

crust thereon so that the asphaltum solution may be applied in a thincoating thereon and kept away from thenon-printing surface of the plate.These three features contribute to the production of a printing platehaving a plane surface thereon wherein the subject or design is clearcut and well defined;

It is obvious that minor changes in the details stated and in thespecific chemicals used and in the order of applying the same may bemade Without departing from the spirit of the invention, as set forth inthe appended claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is

1. The process of making a' printing plate Whichincludes applying to ametal plate a sensitized film capable of being rendered insoluble bylight, exposing the plate under the desired design, washing out theunexposed portions covered by the design, washing said plate with asolution to soften the film, hardening the surface of the film, coat-.sired. design, washing out the unexposed exposed printing surface ofthe metal, hurdening the surfaceofthe film, coating the plate with anacid-resisting substance, and removing the film by acid.

3. The process of making a printing plate which includes applying to ametal plate a sensitized film capable of being rendered insoluble bylight, exposing the plate to a deportions-beneath the design, washingsaid plate with a caustic alkaline solution to soften the film and toclean the exposed printing surface, washing said plate with alcohol toharden the surface of the film, coating the film and printing'surfacewith an acid-resisting substance, and subjecting the plate to a diluteacid solution to remove the film. i

4. The process of making a printing plate which includes applying to ametal plate a sensitized film capable of being rendered insoluble bylight exposing the plate under an original drawing of the desireddesign,

washing out the unexposed portions beneath. the design, washing saidplate with a solution of potassium hydrate, then washing said plate inalcohol, coating the film and printing surface with an asphaltumsolution, subjecting said plate. to a dilute hydrochloric acid to removethe film.

5. The process of making a printing plate which includes applying to ametal plate a. sensitized film capable of being rendered in soluble bylight, exposing the plate under an original drawing of the desireddesign, washing out the unexposed portionbeneath ing said plate with asolution which softens the film and cleanses the exposed printingsurface of the metal printing plate, vi-ashing the plate with alcoholtoremove the dye and to crust harden the film, coating the film andprinting surface with an acid resisting substance and finally subjectingthe plate to a dilute acid to remove the film.

' the design, applying to the film a dye, wash- In testimony whereof, Iaffix my signature l in the presence of two witnesses.

WALLACE W. KIRBY. Witnessesz.

E. H. PARKINB, GRACE P. BRERETON.

